(a) Field of the Invention
The present invention relates to a probe of a scanning probe microscope. More particularly, the present invention relates to a probe of a scanning probe microscope having a field-effect transistor and a carbon nanotube, and a fabrication method thereof.
(b) Description of the Related Art
With the advent of nano-techniques, one of the most frequently used devices utilizing the techniques is the scanning probe microscope (SPM.)
The SPM includes devices for measuring various physical quantities by using a micro probe with a scanning function.
The SPM has a probe with a very sharp tip, a scanner for scanning the probe on a sample, and a control and information processing system for controlling the probe and the scanner and receiving and processing signals.
The SPM has been developed in various forms, and the operational principles of the microprobe are varied according to the physical quantities to be measured. One example of the SPM is a scanning tunneling microscope (STM) that uses a current flowing as a result of a voltage difference between a tip and a sample.
Other examples of the SPM include an atomic force microscope (AFM) that uses atomic power readings between the tip and the sample, a scanning near-field optical microscope (SNOM) that uses wavelengths of visual rays between the tip and the sample, and an electrostatic force microscope (EFM) that uses the electrostatic force between the tip and the sample.
The above-noted SPMs are used to measure general surface properties, and they are also applied to fabrication of new devices. The representative thereof is the future high density data storage system.
As usable quantities of information have been greatly increased, the capacity of information storage devices for storing information has also substantially increased. The most commonly used of the information storage devices is a magnetic information device, that is, a hard disk drive (HDD), and the capacity per unit area of the HDD has been constantly increased through various technical developments.
However, the increase of the above-mentioned capacity is reported to be restricted sooner or later because of superparamagnetic limits.
In order to overcome the superparamagnetic limits, studies on SPM-based the future high density data storage systems, that is, nano-storage devices, have actively progressed. The nano-storage devices vary characteristics of small parts of a medium to store and read information by using a fine probe, thereby enabling atomic-level information storage.
For the purpose of fabricating the future high density data storage systems, studies of the use of various types of SPMs and various information storage media have been researched. Among them, a method of using ferroelectrics as storage media has been repeatedly studied since the first issue by Franke in 1994, because the method has merits of convenient reproduction and usage, quick switching time, and high recording density.
However, the method for performing a reading process, such as the EFM method, is very slow and further requires a lock-in amplifier as shown in FIG. 1, so it is inappropriate for the future high density data storage system that requires a smaller size and high-speed scanning performance.
Therefore, it is essential for the future data storage system to eliminate the above-noted problems in the case of fabricating the probes for precisely measuring external fine electrical signals.
As to prior art for solving the drawbacks, Korean Patent Publication No. 2001-0045981 and Korean Patent Publication No. 2003-0087371 are disclosed.
The inventions use field-effect transistors (FETs) as probes which measure changes of the current flowing between a source S and a drain D when the channel of a gate G is varied because of an external electrical stimulus, in a like manner of general FETs.
That is, electrical characteristics such as surface charges can be measured by measuring the variation of the current between the source S and the drain D since the current is carried by electrical stimuli such as external charges.
However, as shown in FIG. 2, the probe of the invention No. 2001-0045981 has a planar shape and hence it is difficult to fabricate it as an array. In addition, in order to measure fine structures, the sharpness of the tip needs to be of a level of several tens of nanometers, but it is not easy to make the tip satisfy the above-noted level in the above-described structures.
In addition, the invention No. 2003-0087371 has improved upon the planer problem of the invention No. 2001-0045981, but it has a problem of leakage currents and deterioration of the FET characteristic since the FET has a curved form as shown in FIG. 3. Further, since the invention No. 2003-0087371 reduces slope portions more than the end portion of the tip in the case of reducing the size of the tip as shown in FIG. 4, an effect of increasing the distance between the end portion of the tip and the channel is generated (refer to L1 and L2), and hence, reduction of the tip size is restricted.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.